Chemically induced male sterilization using gametocides has been employed in some plant families to effect hybridization. Thus, rows or groups of plants are selected to become the female plants for the production of hybrid seeds. These female plants are rendered male sterile by contact with a selective chemical sterilant or gametocidal compounds. Such rows or groups are interposed with rows or groups of plants selected to perform as male donor plants. Such male donors are not contacted with the gametocide and produce pollen in the normal fashion. This pollen is allowed to contact the female sexual organs of the male sterile female hosts either through wind pollination, hand pollination or through the mediation of insects. If the female hosts are effectively male sterile, self-pollination of such hosts is precluded and uniform, exclusive pollination of such female hosts by the selected male donor plants is ensured. The seeds resulting from such cross-pollination are hybrid in nature and reflect differing male and female parental heritage. Such seeds, when planted and nurtured during subsequent growing cycles, may exhibit hybrid vigor, improved physical traits, and other benefits known to be associated with such hybrid genetics. The publication, "Chemically Induced Male Sterility, a New Tool in Plant Breeding?" F. Wit. Euphytica Vol. 9, No. 1 p. 1 et. seq. and "Evaluation of Certain Chemicals as Selective Gametocides for Wheat", Porter et al. Crop Science p. 381 et. seq. (1961), provides further background information on this method of growing hybrid seeds.
A plant growth regulator, the potassium salt of 3,4-dichloro-5-isothiazolecarboxylic acid, has been suggested as a selective male gametocide for cotton. See, for example, Olvey et al. pre-conference brochure of the 1981 Betlwide Cotton Production Research Conferences and Special Meetings, p. 9. and U.S. Pat. No. 3,341,547 (as to growth regulating activity generally). No method for attaining effective male sterility in cotton while maintaining good female fertility is known to have been disclosed heretofore, however. Furthermore, no effective gametocidal compositions for the hybridization of cotton are believed to be known.